Throughout the arts, there is an ever increasing use of inflatable devices comprising exterior casings or bladders of thin-walled, flexible materials and that are filled with fluid mediums. The bladders or casings of a great number of those inflatable devices are made of soft, flexible and supple substantially non-elastic sheet materials that are not intended to be distended or stretched to any appreciable extent when in use.
In the case of inflatables filled with compressible gases, such as air, it is often possible to gather and/or pinch a portion of a wall of the bladders (or casings) to establish folds when the inflatables are filled to desired extents.
In the case of inflatables filled with substantially non-compressible fluid or liquid mediums, such as water, it is often possible to gather and/or pinch a portion of a wall of the bladders to establish a fold when the inflatables are filled to a desired extent where predetermined, limited slack is let to remain in the bladders.
When inflatables of the general character referred to above are inflated to a desired extent or degree, the walls of their bladders are normally subjected to predetermined tensile forces directed onto and through them by the fluid mediums that fill the bladders.
In the art of waterbeds, the most common type of waterbed includes a single or unitary watermattress structure contained within an upwardly opening frame structure. The watermattress is a bladder-like structure made of thin, flexible and supple plastic, such as sheet polyvinylfluoride. A watermattress, when in use, has or defines vertically spaced horizontal top and bottom walls and vertical side and end walls. A water filler fitting is engaged in and through the top wall, to facilitate filling (and emptying) the watermattress with water. When properly filled with water and ready for use, the watermattress is evacuated of air and is filled with a sufficient volume of water so that the top wall thereof is drawn substantially free of free-standing folds and the like yet is left with a desired amount of slack. The hardness or firmness of the watermattress is determined by the volume of water contained thereby and by the resulting slack that is left to remain in its top wall. In practice, the difference in the volume of water between a soft-filled and firm-filled standard watermattress is often little more than two or three gallons of water.
Another common and widely used type of watermattress, commonly referred to as a "tube-type watermattress" distinguishes from the above-noted common watermattress in that it is made up of an assembly of separate elongate substantially tubular water-filled bladders, or "tubes," that, when in use, are arranged in parallel, side-by-side relationship within the related bed frame structure.
In waterbeds with tube-type watermattresses, the several bladders or tubes are filled with water to an extent that they conform to the interior of their related frame structures and with each other and so that their upwardly disposed portions or top walls occur on the horizontal top planes of the mattress assemblies. That is, they are filled so that when arranged in working position the top wall of one tube does not occur on a horizontal plane that is notably higher or lower than the plane or planes on which the top walls of adjacent tubes occur.
In practice, tube-type waterbed mattresses may include as few as two and as many as twelve tubes. The difference in the volume of water in each tube to establish soft-to-firm filled watermattress assemblies is often little more than two or three cups of water, and a difference of little more than one-half to three-quarters cups of water in adjacent tubes is often sufficient to result in a notable and undesirable difference in the firmness of adjacent tubes. Accordingly, it is extremely important that the tubes in tube-type watermattresses be carefully and accurately filled so that the volume of water in each of the multiplicity of tubes is, for example, no more than one-quarter to one-half cup of water than is contained in each adjacent tube.
The task of accurately filling the tubes of tube-type watermattresses has led to the now accepted and common practice of filling the tubes, outside or remote from their related bed structures and subsequently carrying and properly placing the heavy and difficult-to-handle water-filled tubes within their related bed structures. A special art for filling those tubes has also developed. That art consists of manually elevating and holding one (designated) end of each tube of (a set of like tubes) up so that the tube is suspended vertically while it is being filled with water. Each of the several tubes is filled with water so that the vertical column of water in all of the tubes is the same. To facilitate the above filling procedure, many manufacturers of tube-type watermattresses now imprint water level lines at and along the end portions of their tubes that are to be elevated when being filled. Those water level lines include vertically spaced lines to which the water level within the vertically disposed tubes is to be brought to establish soft, medium and firm watermattress assemblies.
Since the tubes of tube-type watermattress assemblies, when filled, often contain in excess of two cubic feet of water, weight in excess of 140 pounds and are non-rigid "floppy" units prior to being placed in working position, the filling and placement of the tubes is a time-consuming and difficult procedure that, with rare exception, must be performed by large, strong and skilled professional installers, if proper installation is to be performed with reasonable dispatch and with minimum difficulties, hardships and mess.